System for counteracting undesired oscillations in alternating current circuits



Oct. 18, 1932. T BURNS 1,883,536

SYSTEM FOR COUNTERACTING UNDESIRED OSCILLATIONS IN ALTERNATING CURRENT CIRCUITS Filed Nov. 7. 1931 38 /27 I \Z4 T 23 10 5 15 a0-='= :1 13

id 1 l INVENTOR THOMAS H Bum/s ATTORNEY Patented Get. 18, 1932 UNITED STATES,

PATENT OFFICE THOMAS H. BUR-NS, OF MAPLEWOOD, NEW- JERSEY SYSTEM'FOR COTTNTERACTING UNDESIRED OSCILLATIONS IN ALTEBNATING CURRENT CIRCUITS Application filed November 7, 1931. Serial No. 573,667.

The invention relates to a system for the prevention of undesired or stray oscillations or oscillations of regeneration in an alternating current circuit, and more particularlyto the counteracting in electrical circuits, as radio frequency receiving and transmitting circuits, of ob ectionable oscillations set up therein. In tuned radio frequency receiving circuits, for example, such as the typical circuits embodying one or more stages of radio frequency amplification, it frequently occurs in the operation of the same that disturbing oscillations develop as a result of the production of a regenerated wave. These oscillations have a frequency slightly higher or lower than that of the wave the circuit has been tuned or adjusted to; and the resulting heterodyning of these waves of different frequencles produces an audible frequency up to approximately 500 cycles which distorts the output current. Sharply tuning the grid and plate circuits, also, may result in regenerated oscillations, due to magnetic and dielectrio coupling of said circuits.

The system of the present invention contemplates counteracting such undesired 0scillations by associating or capacitatively coupling with a circuit one ormore stabilizing circuits, each consisting of two circuit portions wherein are set up voltages counteracting induced voltages of regeneration developed in the part of said original oscillating circuit with which each respective circuit portion is coupled. Heretofore, it has been proposed to provide in the original circuit an exactly opposed impedance, or to provide therein a definite opposing electromotive force. Both of these expedients, if the adjustments are only slightly out, can be offset. by raising or by lowering the total admittance of the tuned grid circuit and so permit of tuning at twodifi'erent dial settings. The result is broad tuning and inability completely to eliminate incipient undesired oscillations unless a considerable excess of negative impedance and consequent low eificiency are allowed. The novel system on the contrary relies on no exact impedance effect with current variable, nor fixed impedance with its current controlled by some other part of the circuit, due to capacity coupling or direct series connection, but'utilizes an arbitrary fixed impedance and variable current, not controlled by capacity coupling due to neutralization of the capacity coupling nor by direct connection to some part of the circuit, but by a dielectric balance in a tapped capacity system.

The nature of the invention, however, will best be understood when described in connection with the accompanying drawing which is a diagrammatic representation of a typical radio receiving circuit embodying. for example, two stages of radio frequency amplification and a detector, with the novel stabilizing circuit associated with grid cir-' cuits thereof.

Referring to the drawing, the invention is illustrated as applied to a tuned radio fre quency circuit embodying by Way of example two stages of radio frequency amplification; and to this end comprises generally the first transformer 10, amplifying tubes 11 and a detector tube 12, with intermediate amplifying transformers 13 and the tuning condensers 14. The particular circuit set forth is shown merely by Way of example; and it is to be understood that the invention is not restricted to the particular character of circuit shown but is applicable to various circuits wherein disturbing oscillations may develop due tocertain conditions or characteristics inherent in the circuit or from an outside source.

To overcome the efiect of such undesired oscillations there is arranged to be associated with said circuitthe hereindescribed stabilizing circuit, which may be applied in mulso i tiple when additional stages of amplification u the capacity 20 and a junction point 25. Two

closed circuit portions arethereby formed inductance 23 and the two parallel paths through capacity half 24, and capacity half 27 and inductance or impedance 22 to the junction point 25 as well as leads to effect the connections. The respective values of the different capacities and inductances associated therewith in the stabilizing circuit will, of course, depend on the constants of the operating circuit.

As set forth, the stabilizing circuit consists of two portions each adapted to counterbalance an induced voltage such as may be caused by regeneration in their respective circuits to which they are coupled through the coupling capacities 30. With an instantaneous voltage increase at point 28, dielectric current will flow equally from point 28 through the parallel paths 24: and 27.22 due to their equivalent impedances, dielectric flux in capacity half 24 will increase and dielectric fiuX in capacity half 27 will decrease by equal amounts (equivalent to the voltage increase at point 28). The total flux remains the same, as does the voltage across capacity 21.

Thus, the voltage Variations across capacity 20 do not directly aflect the voltage across capacity 21. An electrical balance is brought about not through a voltage or electrostatic relation between the two circuit portions of the stabilizing circuit but by an independent current regulation.

VVhilethe embodiment of the invention is herein shown as applied specifically to a radio frequency circuit, it is to be understood that the same is equally applicable to the counteracting of undesired or stray oscillations of regeneration in audio frequency circuits.

I claim:

1. In a systein for counteracting undesired oscillations in aradio frequensy circuit including a tuning portion: a stabilizing circuit capacitatively coupled thereto and through a junction point, said circuit including two closed circuit portions each containing a condenser, the one condenser being connected to the other substantially at its midpoint to form therewith the one closed circuit portion; an inductance in said closed circuit portion; and an inductance in the other closed circuit portion which includes the divided condenser and the junction point.

2. In a system for counteracting undesired oscillations in a radio frequency circuit including a tuning portion: a stabilizing circuit capacitatively coupled thereto and through a junction point, said circuit including tWo closed circuit portions each containing a condenser, the one condenser bein bridged with an inductance to form one close circuit portion; the other condenser being connected substantially at the midpoint of the first condenser to form therewith and with the bridged inductance the other closed circuit portion, and an inductance in the last closed circuit portion.

3. In a system for counteracting undesired oscillations in a radio frequency circuit of two stages of tuned radio frequency amplification a stabilizing circuit including two closed circuit portions each containing a condenser capacitatively coupled respectively to two of the grid circuits of the radio frequency circuit and also through a junction point; variable inductances included in both of the circuit portions and leads connecting the two portions to each other in manner such that the condenser of the one circuit portion is connected substantially to the midpoint of the condenser of the other circuit portion.

a In testimony whereof I afiElX my signature.

THOMAS H. BURNS. 

